I look on Vortex but only those BOZ bots are on half the time... It's sad. I'm not a co-op kinda guy, I love the competitive side of things. I'd love to get a regular CTF game in Veins going again, that was still a popular map back only a few years ago.

Check around 4 P.M. EST. We had 4 in BI3 DRH for 2 hours 12-31-17. Crazy good fun with Mental Floss,LEON, Alexander and I (mickey1). 3 Tanks and me in a Black Pyro. I had to stop using the Phoenix for the extra ammo and agility. Speed will just get you ganked faster; the AB, forget about it except in a dogfight.

It's not a hard-and-fast rule, just a general observation
The D3 single-player mode has some gameplay issues (mainly that almost all the robots are hard to hit), but if you have the game it's probably at least worth trying.

Is it possible to play fun games without strongly participating in ranking games/tournaments? I am interested in occasionally playing multiplayer (D1/D2) games but don't care about ranks. And I cannot plan for sure whether I will be able to play at particular day and particular time.

Do you mean anyone can see a game and join? Because frankly both on Descent Rangers and DCL, I was pissed off by the procedure for becoming a member, I think it is more complex than one used by Google to hire a leading Research Engineer . Surely more complex than in Intel where I worked. Yes I understand that people are to comply to some rules, should be sane and not be cheaters/trolls, but the application procedure looks overwhelming - especially in such a small community... And do I absolutely need Retro mod to play, or Rebirth 0.58.1 is ok?

Yeah the games I'm talking about you don't need to be a member of anything. If the game is open, it's probably free to join (unless someone left something open by mistake. But the title will usually tell you if it's a Rangers or DCL game... if it doesn't, it's the host's fault for neither locking it down nor making it clear ).

Retro is usually necessary, though, because it made protocol modifications to reduce latency (among other things) that base Rebirth doesn't support. The most frequently-used versions are 1.4.5a for D1 and 1.4.X3 for D2, although that might change in the next few months because roncli is doing some work on it.